542 HISTORICAL GEOLOGY. 



the "millstone grit" of Eaton. It was formerly much used for making the " Esopus 

 millstones," so named from Esopus, an early name of Kingston ; and at Ellenville, for 

 glass-making. It is intersected by quartz veins ; and niines of lead and zinc have been 

 worked in it at Ellenville, Wurtsborough, and elsewhere, which have yielded remarkable 

 geodes of quartz crystals, with crystals of lead ore (galena), sphalerite, chalcopyrite, and 

 other minerals. 



The Medina sandstone, where fullest developed in New York, includes, according 

 to Hall, four divisions, as follows : — 



(4) Red marl or shale and shaly sandstone, resembling No. 2, below ; banded and 

 spotted with red and green. 



(3) Flagstone, — a gray, laminated quartzose sandstone, called " gray band." 



(2) Argillaceous sandstone and shale, red, or mottled with red and gray. 



(1) Greenish gray sandstone, graduating below into the Oneida conglomerate, the 

 "gray band" of Eaton. 



In the Genesee section (page 91), the strata 1 and 2 correspond to the Medina ; 3, 4, 

 5, 6, to the Clinton group ; and 7, 8, to' the Niagara shales and limestone. 



In Canada the Medina beds, besides existing in Ontario, occur south of the St. Law- 

 rence, over a few areas east and northeast of Lake St. Peter. 



The Oneida conglomerate disappears before reaching the southern border of Pennsyl- 

 vania, and the passage from Hudson into the red Medina is imperceptible. Hudson fossils 

 continue far up into the Medina in Bedford County. {Bep. T 2, Penn. Surv., pp. 91 and 

 92, J. J. Stevenson.) This condition becomes more striking in southwest Virginia beyond 

 the New River, where Hudson forms occur up to within 100' of the white Medina. (J. J. 

 Stevenson, Proc. Amer. Phil. Soc, xxiv., 85, 87, 94; and xxii., 142, 150.) A peculiarity 

 of the Upper or white Medina in Pennsylvania and southward is, that exposure to atmos- 

 phere polishes it ; all other sandstones there are roughened by exposure. (J. J. S.) 



2. Clinton Group. — This is the "Protean group" of the JV. Y. Annual Geological 

 Beports of 1836-1840. The sandstone of the Clinton epoch in New York is often quite 

 hard ; and much of it has the surface uneven from knobby and vermiform prominences, 

 some of which are attributed to Eucoids. 



(a) Interior Continental basin. — On the Genesee River, at the falls near Rochester, 

 the Clinton group consists of: (1) 24' of green shale, of which the lower part is shaly 

 sandstone and the upper part an iron-ore bed ; (2) 14' of limestone, called Pentamerus 

 limestone, from a characteristic fossil; (3) 24' of gree)i shale; (4) 18i' of limestone, 

 called the Upper limestone. 



On the Niagara (see section, Fig. 738, page 540) there is shale 4', loithout the iron ore, 

 overlaid by limestone 25', the limestone corresponding to the three upper divisions, and 

 its upper 20' to the upper limestone. To the eastward, in Oneida, Herkimer, and Mont- 

 gomery counties, the rock is 100'-200' thick, and includes no limestone, though partly 

 calcareous. The group consists of shale and hard grit or sandstone, in two or more alter- 

 nations, along with two beds of the iron ore. Near Canajoharie — which is not far from 

 its eastern limit — the formation has a thickness of 50'. In Starkville, Herkimer County, 

 the rock contains a bed of gypsum. 



North of Lake Huron, the Clinton beds occur along the Manitoulin Islands, Drummond 

 Island, and 20 miles to the westward. 



(6) Appalachian region. — The relations of the Clinton of Pennsylvania and the 

 country southward to that of central New York are not determined in detail. The rocks 

 in Pennsylvania are shales, olive to almost black, with some sandstones and beds of calca- 

 reous iron ore. The series is persistent, northwestwardly, to the last exposures, almost at 

 the easterly foot of the Alleghany Mountains. Its subdivisions are : (1) Reddish to olive 

 shales, 100' to 700' ; (2) iron sandstone, 5' to 50' ; (3) shales, 200' to 675' ; (4) iron 

 sandstone, 10' to 20' ; (5) shales with calcareous layers, 100'. The whole thickness is 

 from 900' to 1000'. A commingling of Clinton and Niagara forms occurs in the upper 



